Previously, even though I used Emacs as an editor, the idea of moving functions that correspond to applications (like mail reading) into an editor looked clunky and even dirty to me.
But I grew disillusioned of the Unix ethos. While it works well for composing very simple programs, it fails to deliver on most other things. For example, Mutt is a great mail user agent. But it is very difficult to customize beyond its author's original intentions using its own little configuration DSL. And scripting it from your shell does not lead anywhere. This happens with many other nice Unix utilities.
In contrast Emacs, understood as a text-mode Lisp machine, is at odds with this approach. The code you write is as first class as the code you run from whatever module you import. Everything is alive, integrated, and can be changed.
As a programmer, I am moving towards more and more abstract application domains for the same reason. Mathematica, PyMC or Scheme allow me to ignore all the horrid details the OP describes and work at a higher level.